Bipolar transistors are electronic devices with two P-N junctions that are in close proximity to one another. A common bipolar transistor has three regions: i) an emitter, ii) a collector, and iii) a base present between the emitter and the collector. If the emitter and the collector are doped with an n-type dopant and the base is doped with a p-type dopant, then the device is an “NPN” transistor. Alternatively, if the emitter and the collector are doped with a p-type dopant and the base is doped with an n-type dopant, then the device is a “PNP” transistor.
Despite the prevalence of CMOS FETs, bipolar transistors have superior device attributes in some areas, especially for analogue and power gain applications. Conventional bipolar devices require abrupt emitter-to-base junctions and well controlled base region lengths and are typically not scaled for circuit density of CMOS structures.
Therefore, improved bipolar transistor designs and techniques for fabrication thereof would be desirable, especially when compatible with CMOS FET fabrication processes.